The present invention refers to a device for changing the under thread bobbin of an industrial embroidery or sewing machine of a type having a shuttle driven by a hook shaft.
In general, an embroidery or sewing machine requires a removal of an under thread bobbin from the shuttle for replacement by a new bobbin when the under thread is spent and thus the bobbin is empty or when the under thread ruptures during stitching operation. Replacement or exchange of the bobbin can only be carried out in idle state of the machine. Typically, the shutdown of the machine is effected automatically and is triggered by an under thread guard or detector. When the machine spins at a normal speed of 700 rpm and when using a standard under thread bobbin of approximately 100 m thread length, the under thread is usually used up already after about 45 minutes.
Even though, a needed replacement of a spent under thread bobbin during shutdown of the machine can be executed by skilled personnel in about five to eight seconds, these shutdown periods have a significant impact on industrial embroidery or sewing machines because these types of stitching machines have normally 10 to 20 stitching heads operating at a same time. Thus, when the under thread is used up on the bobbin of one stitching head, operation of all stitching heads must be shutdown. This means, for example in a stitching machine with twenty heads, a loss of three minutes is to be accepted in production time per work hour during periodic change of all under thread bobbins.